Enhance email notification for input devices

InputDevice.WaitingFileCount does not show up currently as a column to be selected for input devices email notification. I understand why it was not added because it could be sending some false notification if the input device has a long polling interval.

It would be nice tho to add a property for input devices that logs when was the last time it polled for files and then under conditions if we could say current time > last polled time ( even better if we could do like + n minutes ) then the customers can get alerted when they have waiting files under input devices that was not picked up for whatever reason.